Immigration Minister Philip Ruddock said the large majority of asylum seekers now in detention centres were not genuine refugees, with the lack of new boat arrivals in recent months meaning a greater percentage of detainees had been processed compared with other times.

"We are now dealing with a population ... (who) are not, in the main, people who have bona fide asylum claims," Mr Ruddock told reporters in Sydney. He said of 1700 people being held across the country, 700 had no claims and were being held for removal, while another 700 had had their claims rejected, but were going to appeal those decisions.

"You come to a residue of about 300 people and in the main they are people, even if they have claims worthy of consideration, who have not been security cleared," Mr Ruddock said.

He said a few of the 700 who were testing their decisions through the courts may later be found to be refugees.